Up until now, small bookbinding apparatuses for binding a book in a simple manner by applying an adhesive to a sheet stack have been popularly used in an office, school, home, etc. Most of such bookbinding apparatuses require a cover specifically designed for the apparatus, provided with a hot-melt adhesive applied in advance to an inner face of its spine. A sheet stack enclosed in such cover is set in the bookbinding apparatus, and a heater of the apparatus melts the adhesive provided inside the cover, thereby bonding the sheet stack and the cover together.
However, since a specifically designed cover having a predetermined spine width is used in this type of bookbinding apparatus, a thickness of the sheet stack to be bound does not always fit the spine width of the cover. In such a case a gap is produced between the cover and an uppermost page of the sheet stack, thereby degrading the finish of the book. Besides, this type of bookbinding apparatus cannot be used for pad binding, which is a method of binding a paper pad coated with an adhesive without enclosing in a cover.
Accordingly, in order to bind a cover in accordance with a thickness of a sheet stack, or to perform the pad binding, a bookbinding apparatus that applies a melted adhesive to an end face of a paper pad with a roller and solidifies the adhesive on a flat plate has come to be used. As an example of such type of bookbinding apparatus, Japanese unexamined patent publication No.H09-156249 discloses a bookbinding apparatus that applies an adhesive to a lower face of a sheet stack by conveying the sheet stack held by a paper holder so as to pass over a coating roller.
However, in this bookbinding apparatus, since the sheet stack moves back and forth over the roller together with the paper holder, in a longitudinal direction along the back of the sheet stack, the apparatus has to be at least wider than a double of the length of the sheet stack; therefore it is difficult to make the apparatus smaller in size. On the other hand, some bookbinding apparatuses are designed such that the sheet stack moves back and forth in a widthwise direction (i.e. thicknesswise direction) on a roller longer than a length of the sheet stack, to apply an adhesive to the back of the sheet stack. Such a bookbinding apparatus can be made smaller in widthwise dimension, since the sheet stack moves in a widthwise direction (thicknesswise direction) thereof.
However, these types of bookbinding apparatus are generally provided with an adhesive tank having a large capacity, to replenish the adhesive less frequently. Especially in case of a bookbinding apparatus that moves a sheet stack in a widthwise direction, since the roller has to be sufficiently long, the adhesive tank for retaining the adhesive to be applied to the sheet stack with the roller naturally has to be long, and hence has a large capacity. And in case where the adhesive tank is large, it takes a longer time in melting the adhesive retained therein, and therefore a start-up period is prolonged, before entering a stand-by state where the apparatus becomes ready to operate. Besides, a larger amount of adhesive volatilizes from the adhesive tank, resulting in increase of smell of resin or rubber contained in the adhesive melted by a high temperature.
Accordingly, it is an object of the present invention to provide a small-sized bookbinding apparatus that can quickly start up to enter a stand-by state.